diff --git a/bec_widgets/widgets/plots/waveform/waveform.py b/bec_widgets/widgets/plots/waveform/waveform.py
index 3d6127dc..1c075029 100644
--- a/bec_widgets/widgets/plots/waveform/waveform.py
+++ b/bec_widgets/widgets/plots/waveform/waveform.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import json
-from typing import Literal
+from typing import Any, Literal
 
 import lmfit
 import numpy as np
@@ -163,7 +163,7 @@ class Waveform(PlotBase):
         self._async_curves = []
         self._slice_index = None
         self._dap_curves = []
-        self._mode: Literal["none", "sync", "async", "mixed"] = "none"
+        self._mode = None
 
         # Scan data
         self._scan_done = True  # means scan is not running
@@ -1139,7 +1139,7 @@ class Waveform(PlotBase):
             QTimer.singleShot(100, self.update_sync_curves)
             QTimer.singleShot(300, self.update_sync_curves)
 
-    def _fetch_scan_data_and_access(self):
+    def _fetch_scan_data_and_access(self) -> tuple[dict, str] | tuple[None, None]:
         """
         Decide whether the widget is in live or historical mode
         and return the appropriate data dict and access key.
@@ -1153,7 +1153,7 @@ class Waveform(PlotBase):
             self.update_with_scan_history(-1)
             if self.scan_item is None:
                 logger.info("No scan executed so far; skipping device curves categorisation.")
-                return "none", "none"
+                return None, None
 
         if hasattr(self.scan_item, "live_data"):
             # Live scan
@@ -1169,7 +1169,7 @@ class Waveform(PlotBase):
         """
         if self.scan_item is None:
             logger.info("No scan executed so far; skipping device curves categorisation.")
-            return "none"
+            return
         data, access_key = self._fetch_scan_data_and_access()
         for curve in self._sync_curves:
             device_name = curve.config.signal.name
@@ -1177,9 +1177,8 @@ class Waveform(PlotBase):
             if access_key == "val":
                 device_data = data.get(device_name, {}).get(device_entry, {}).get(access_key, None)
             else:
-                device_data = (
-                    data.get(device_name, {}).get(device_entry, {}).read().get("value", None)
-                )
+                entry_obj = data.get(device_name, {}).get(device_entry)
+                device_data = entry_obj.read()["value"] if entry_obj else None
             x_data = self._get_x_data(device_name, device_entry)
             if x_data is not None:
                 if len(x_data) == 1:
@@ -1217,7 +1216,8 @@ class Waveform(PlotBase):
                 if self._skip_large_dataset_check is False:
                     if not self._check_dataset_size_and_confirm(dataset_obj, device_entry):
                         continue  # user declined to load; skip this curve
-                device_data = dataset_obj.get(device_entry, {}).read().get("value", None)
+                entry_obj = dataset_obj.get(device_entry, None)
+                device_data = entry_obj.read()["value"] if entry_obj else None
 
             # if shape is 2D cast it into 1D and take the last waveform
             if len(np.shape(device_data)) > 1:
@@ -1549,15 +1549,21 @@ class Waveform(PlotBase):
             if access_key == "val":  # live data
                 x_data = data.get(x_name, {}).get(x_entry, {}).get(access_key, [0])
             else:  # history data
-                x_data = data.get(x_name, {}).get(x_entry, {}).read().get("value", [0])
+                entry_obj = data.get(x_name, {}).get(x_entry)
+                x_data = entry_obj.read()["value"] if entry_obj else [0]
             new_suffix = f" (custom: {x_name}-{x_entry})"
 
         # 2 User wants timestamp
         if self.x_axis_mode["name"] == "timestamp":
             if access_key == "val":  # live
-                timestamps = data[device_name][device_entry].timestamps
+                x_data = data.get(device_name, {}).get(device_entry, None)
+                if x_data is None:
+                    return None
+                else:
+                    timestamps = x_data.timestamps
             else:  # history data
-                timestamps = data[device_name][device_entry].read().get("timestamp", [0])
+                entry_obj = data.get(device_name, {}).get(device_entry)
+                timestamps = entry_obj.read()["timestamp"] if entry_obj else [0]
             x_data = timestamps
             new_suffix = " (timestamp)"
 
@@ -1584,7 +1590,8 @@ class Waveform(PlotBase):
                 if access_key == "val":
                     x_data = data.get(x_name, {}).get(x_entry, {}).get(access_key, None)
                 else:
-                    x_data = data.get(x_name, {}).get(x_entry, {}).read().get("value", None)
+                    entry_obj = data.get(x_name, {}).get(x_entry)
+                    x_data = entry_obj.read()["value"] if entry_obj else None
                 new_suffix = f" (auto: {x_name}-{x_entry})"
         self._update_x_label_suffix(new_suffix)
         return x_data
@@ -1637,7 +1644,7 @@ class Waveform(PlotBase):
             self.update_with_scan_history(-1)
             if self.scan_item is None:
                 logger.info("No scan executed so far; skipping device curves categorisation.")
-                return "none"
+                return None
 
         if hasattr(self.scan_item, "live_data"):
             readout_priority = self.scan_item.status_message.info["readout_priority"]  # live data